Cancer remains a tremendous challenge in the healthcare industry worldwide, in part, because cancer cells possess the ability to evade the host immune system. Such ability has been understood to be the result of inhibition and/or down-regulation of anti-tumor immunity. Still, development of useful in vivo systems to optimally determine the therapeutic potential of new cancer therapeutics and/or therapeutic regimens that are designed to activate and/or promote anti-tumor immunity and determine the mechanisms of how cancer cells provide inhibitory signals to immune cells, in particular, T cells, is lacking. Such systems provide a source for assays for assessing the therapeutic efficacy of candidate agents that promote an anti-tumor environment in vivo.